This invention relates to joints for rotating members, and more particularly to a flexible coupling in which misalignment is compensated for by some of the material in the joint being flexible.
When rotary movement is transferred along a drive shaft or similar member, misalignment of driving and driven members my require some flexibility in the joint. In some applications, this flexibility is accomplished by allowing component parts to move relative to one another across bearing surfaces. A typical application of this is a drive train in which universal joints and splined shafts allow for angular and axial displacement of the drive train components. A drive shaft itself maybe flexible, although this can create problems in that the mass of the drive shaft combined with the flexibility can create a dynamically unstable condition when the drive shaft is expected to operate at significant rotational speeds. Flexible portions may be placed near stabilized bearing supports in order that such dynamic instability does not occur. This invention relates to such flexible portions, called flexible couplings.
In the prior art, flexible couplings have been formed from thin metal diaphragms extending radially from adjacent drive shaft portions, with pairs of the diaphragms being joined at the outer circumference. Such an arrangement is shown in U.S. Pat. No. 4,276,758, assigned to the assignee of the present invention. Specifically, in the prior art arrangement shown in that patent, a pair of drive shaft sections are joined by a pair of discs extending radially outwardly from the drive shaft sections. The discs taper toward the perimeter, where (at the perimeter) the discs have a thickened portion. The thickened portion serves as a spacer for keeping the remainder of each disc separate from the other. The two discs are joined at the thickened portion, i.e., at the perimeter. The amount of misalignment and/or axial movement that can be tolerated between the two shafts is a function of the stresses these movements develop within the disc or diaphragm. Each disc or diaphragm deforms equally in the total movement. The total amount axial and/or angular misalignment this type of disc can withstand is relatively small. If greater amounts of misalignment are to be compensated for, additional sets of discs are required.
It is accordingly an object of the present invention to provide a flexible coupling or flexible shaft end portion, which does not rely on rubbing, contacting or bearing parts to transmit drive force. It is desired that such a flexible coupling be able to compensate for alignment errors which are much greater than those which can be compensated for with a disc-type flexible coupling. It is further important that such a flexible coupling have an extended lifetime. This means that the flexible coupling must be able to flex a large number of times and must be able to withstand the same continuous and intermittent loads as the rest of its associated drive train. It is a further object to provide a flexible coupling which can handle extreme misalignments when the extreme misalignments occur and which does not require a significant amount of maintenance.